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Response mechanism of extracellular polymers in the remediation of chromium pollution by carbonate mineralizing bacteria

Summary

Certain bacteria can help clean up chromium pollution by producing protective coatings made of sugar and protein molecules. When exposed to high levels of chromium, these bacteria produce more of these protective coatings, which trap and neutralize the toxic metal. The coating changes its composition to better bind chromium, and the protein structure becomes more porous to catch more metal. This research shows how nature can be used to clean up contaminated environments.

Background

Heavy metal pollution, particularly trivalent chromium (Cr(III)), poses significant environmental and health risks. Bioremediation using microbial-induced carbonate precipitation (MICP) has emerged as a sustainable approach for metal remediation. However, the specific role of extracellular polymers (EPS) in this process remains poorly understood.

Objective

This study investigates the adaptation mechanisms of carbonate mineralizing bacteria to Cr(III)-contaminated environments, with emphasis on the role of EPS in Cr(III) remediation and how EPS composition and structure change in response to varying Cr(III) concentrations.

Results

Cr(III) removal efficiency was nearly 100% at concentrations up to 1000 mg/L but decreased to 64.85% at 3000 mg/L, demonstrating bacterial tolerance. EPS production significantly increased with Cr(III) stress. Polysaccharide and protein contents in EPS increased, with mannose content rising and galactose decreasing. Protein secondary structure showed decreased α-helix and increased β-sheet and random coil structures.

Conclusion

EPS plays a crucial protective role in Cr(III) bioremediation through increased production and structural modifications. Mannose emerged as a key monosaccharide for Cr(III) binding, while protein structural changes enhanced metal ion interaction. These findings provide new insights for developing more effective bioremediation strategies for chromium pollution.
  • Published in:RSC Advances,
  • Study Type:Experimental Research,
  • Source: PMID: 40364817, DOI: 10.1039/d5ra01916h
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